Features On Demand
You need OSBuilder 19.1.17+ for this to function properly
To enable Features on Demand, you will first need to Download and extract an ISO from MVLS. Before getting started, make sure you read and understand what new changes there are with Features on Demand for Windows 10 1809
In Microsoft Volume Licensing Service Center I search for 'Windows 10 Enterprise Features on Demand'. For Windows 10 1809 I see that there are two ISO's that were "Updated Sept '18". These ISO's are the ones I need to download (keep reading first)
I can now download the ISO's to my OSBuilder\Content\IsoExtract directory
The reason this directory is called IsoExtract is because that is what I need to do to this ISO to use it. You can either mount the ISO and copy the files (with the structure intact) or use something like 7-Zip to extract the ISO
When looking in FOD Disc 2, I see that it is only Retail Demo content, so unless I'm Best Buy, there is no need to even use this Disc, so I'll delete it
Leaving only FOD Disc 1, which I will give a friendly name, making sure to include the ReleaseId and the Architecture

New-OSBuildTask

When creating a New-OSBuildTask, I will be prompted to select Features on Demand to include in my OSBuild
See bottom for installing the Windows 10 1809 RSAT Capability

Language Features

I will also receive a prompt to select Language Features on Demand. I don't want these enabled, so I'll press Cancel to skip
If you never plan on using the Language Features On Demand, simply delete the associated CAB files

New-OSBuild

When I create a New-OSBuild, the Features on Demand I selected in my Task will be installed automatically

Results

Easy enough!

Additional Resources

For help installing the Windows 10 RSAT Capability from the Features on Demand ISO, refer to the following Guide